There have been commercially introduced increasing numbers of applications for recognizing the vehicle surrounding environments by a camera mounted in a vehicle and devices equipped with the applications. In particular, it is expected that these products will be applied to preventive safety technologies for prevention of a contact with an object and vehicle control technologies for autonomous running, using the recognition results of surrounding environments. The application of the surrounding environment recognition products to these kinds of technologies require high reliability in the recognition of surrounding environments.
JP 2005-214914 A (PTL 1) discloses a technique for acquiring a pair of images by stereo cameras, detecting a three-dimensional object based on distance data obtained from the pair of images, and calculating the moving speed of the three-dimensional object based on an optical flow (motion vectors) of the three-dimensional object obtained from one of the pair of images.